Electromagnet for lifting large loads of fine-grained ferromagnetic substances



March 5, 1968 DIETZEL ET AL 3,372,357

ELECTROMAGNET FOR LIFTING LARGE LOADS OF FlNE-GRAINED UBSTANCES FERROMAGNETI C S Filed Feb. 23, 1966 INVENTORSI KARL D/ETZEL 'ULP/CH VE/EL United States Patent 3,372,357 ELECTROMAGNET FOR LIFTING LARGE LOADS 0F FINE-GRAINED FERROMAG- NETIC SUBSTANCES Karl Dictzel, Krefeld-Urdingen, and Ulrich Veiel, Krefeld- Bockum, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Feb. 23, 1966, Ser. No. 529,385 Claims priority, application Germany, Feb. 25, 1965, F 45,357 6 Claims. (Cl. 335291) ABSTRACT OF THE DISCLGSURE Electromagnet without an iron core for lifting heavy loads of fine-grained ferromagnetic substances, including a solenoid composed of a spool having its winding in the form of a hollow cone expanding or diverging in the direction of the material to be lifted thereby, such that the magnetic field strength thereof increases along the axis of rotation of said core towards that end which is remote from the material to be lifted.

The present invention relates to a new construction for lifting magnetic substances.

In industry pot-shaped magnets are used for certain purposes such as for lifting such things as iron filings and nail tips. By the nature of their construction, these mag nets operate at optimum efficiency only when they are used for lifting blocks, metal sheets or discs. For lifting iron filings or nail tips, these magnets do not have the desired elficiency because the material collects only in the air gap of the magnet, and owing to the special construction of the magnet, this air gap is relatively narrow. For this reason, the load of iron filings or nail tips on a potshaped magnet consists substantially of a toroidal beardlike cluster arranged around one pole. In addition these magnets are very heavy in comparison with the load lifted.

It is also known to make a load-lifting magnet without an iron core, but in such a magnet, the structural features of pot-shaped magnets are on the whole nevertheless retained (German Patent 425,872). Although such magnets are less heavy than pot-shaped magnets, especially if they are made cylindrical as in German Patent 425,872, they cannot lift heavy loads of fine-grained ferromagnetic substances such as iron powder. The quantity of material which they are capable of lifting can be increased only by increasing the diameter of the magnet, but this increase in diameter is limited by the width of railway trucks, ships etc. When a magnet of the type mentioned in said German patent is used for lifting such fine-grained substances, only a small beard-like cluster is formed under the coil. A certain amount of iron filings is deposited along the walls of the cylindrical magnet, but the interior of the magnetic coil is not filled to the optimum extent with these filings. If in addition a cylinder consisting substantially of iron is placed on the magnetic coil, the efficiency is very greatly impaired because not only is the external path of the magnetic field lines increased but in addition the magnetic field lines slip over the soft iron and are scattered at the edges of the iron.

It is the object of the invention to ensure not only that all the magnetic field lines are used for lifting the fine iron material but also that a magnet is obtained of a suitable construction so that the filings drawn into the interior of the substantially core-less solenoid are packed to the same density as they could be put in mechanically if the magnet were not switched on.

electromagnetic large loads of fine-grained ferroaluminum winding,

I 3,372,357 Patented Mar. 5, 1968 Another object of the invention is to provide that the material to be lifted can be lifted to'a sufiicient height without great additional expenditure. The subject of the invention is a solenoid which expands conically in the direction of the material to be lifted and in which the winding of the coil is so formed that the magnetic field strength increases along the axis of rotation in the direction towards that end which is remote from the material to be lifted. If the conical solenoid has a fixed predetermined maxirnum diameter and the height of the solenoid is of the same order of magnitude as its diameter, a sufficiently powerful force will be exerted from the upper end to the filings situated at the lower end.

Owing to the conical shape of the solenoid and owing to a suitable arrangement of the winding of the coil, the field strength in the upper part will be at least twice that in the lower part. When the current is switched on, the filings are lifted, and an acceleration in the upward direction is imparted to them by the increase in the field strength. Since the solenoid is cone-shaped so that its opening is smaller at the top than at the bottom, the upper part of the coil is filled first and then the middle part and lastly the lower part, and this construction has the effect that when the current is switched on, the material inside the coil is packed to the same density as the unmagnetized filings still on the truck. It is therefore possible to calculate the quantity of load lifted from the internal volume of the solenoid. In order to increase the load still further, it is necessary first to ensure that no field lines are lost by scattering and that these field lines which leave through the top of the open part of the solenoid are returned downwards along the shortest path. It is therefore another feature of the invention to surround the solenoid on the outside only with a jacket of soft iron, which may if desired be conical, this jacket extending as far as the upper opening of the solenoid. This measure has the effect that it is possible to lift an additional quantity of iron filings in the form of a toroidal cluster familiar from potshaped magnets. Moreover, an arrangement of this kind has the advantage that the entire magnet is shielded against impact. A magnet so constructed is capable of lifting up to of its own weight in fine iron filings whereas the ratio of load to dead weight of the magnet in German Patent 425,872 is not greater, in spite of its much lower dead weight, than in a pot-shaped magnet of modern construction which has a high dead weight.

The accompanying drawing shows diagrammatically an embodiment of the invention by way of example. In this drawing, 1 is the soft iron jacket, 2 the copperor 3 the spool body of nonmagnetic material and 4 the retaining ring for the spool, also of nonmagnetic material. A construction in which the ratio of lower opening, i.e., internal diameter to height is about 1:1 has proved to be particularly effective. However, this ratio is not essential.

It is preferable to round off the corners indicated in the drawing. The jacket of soft iron should be about 2 to 3 times as thick at the top, i.e. at the smaller opening, as in the actual cone jacket, in order to reduce the resistance to be encountered by the magnetic lines of force.

We claim:

1. Electromagnet without an iron core for lifting heavy loads of fine-grained ferromagnetic substances, which comprises a solenoid composed of a spool having its winding in the form of a hollow cone of substantially constant thickness expanding uniformly and continuously throughout from one axial end to the other axial end thereof in the direction of the material to be lifted thereby, the axial height and maximum internal diameter of said hollow core being of substantially the same order of magnitude, such that the magnetic field strength thereof increases correspondingly uniformly and continuously throughout along the axis of rotation of said cone towards that end which is remote from the material to be lifted.

2. Electromagnet according to claim 1, wherein said winding is so formed that'the magnetic field strength is at least twice as high at the remote end of the solenoid, measured at the axial center of said hollow cone, as at the axial center at the'corresponding end facing the material to be lifted.

3. Electromagnet according to claim 1, wherein said solenoid is open atthe remote end thereof and is in the form of a truncated cone.

4. 'Electromagnet according to claim 1, wherein said solenoid is surrounded on the exterior thereof with a jacket of soft iron.

-5. Electromagnet without an iron core for lifting heavy loads offine-grained ferromagnetic substances according to claim 1, which comprises a solenoid composed of a spool having its winding inv the form of a hollow truncated cone of substantially constant thickness expanding uniformly and continuously throughout from one axial end to the other axial end thereof in the direction of the material to be lifted thereby and having correspondingly a smaller open upper end and a larger open lower end, the axial height of said cone and the internal diameter of said larger open lower end being of substantially the same order of magnitude, such that the magnetic field strength of said solenoid increases correspondingly uniformly and continuously throughout along the axis of rotation of said cone in the direction from said lower end to said upper end.

6. Electromagnet according to claim 5, wherein said solenoid is surrounded on the exterior thereof with a jacket of soft iron.

References Qited UNITED STATES PATENTS 835,942 11/1906 Eastwood a 335-291 2,438,985 4/1948 Ambrose 336-231 X FOREIGN PATENTS 35,812 8/1885 Germany.

BERNARD A. GILHEANY, Primary Examiner. G. HARRIS, Assistant Examiner. 

